Magnetically actuated pushbutton switches have a metal armature normally held spaced from switch contacts by a magnet. Pushing on the armature causes it to snap free of the magnet and close the switch contacts by shorting them. Release of the actuating pressure allows the magnetic force to withdraw the armature from the contacts to reopen the switch. The switches typically are made in panels having a non-conductive substrate with electrical contacts formed thereon. A non-conductive spacer layer lies on the substrate with openings therein exposing the contacts. A sheet magnet overlies the spacer with the armatures underneath the magnet layer in the spacer openings. The armatures preferably have actuating buttons that protrude through apertures in the magnet layer. Most often the magnet layer itself is covered by a membrane or the like, the upper surface of which carries suitable graphics. The benefits of magnetically-actuated pushbutton switches have been demonstrated in U.S. Pat. Nos. 5,523,730, 5,666,096, 5,867,082 and U.S. patent application Ser. No. 09/160,645, filed Sep. 25, 1998, the disclosures of which are incorporated herein by reference.
Although the pushbutton switch as shown and described in the foregoing patents is very robust and easy to manufacture, relative to its counterparts, certain improvements in the manufacturing process are addressed by the present invention. The most difficult and expensive process in the manufacture of the described pushbutton switches is assembling all of the individual layers consistently. This can be a problem around the individual switch areas where the alignment with the armature is critical. Using pins to align the individual layers relative to each other is adequate to assemble a magnetically actuated pushbutton switch, although it is most advantageously done with special assembly apparatus. Tolerances are always a problem, however. As the overall size of the switch panel increases, the tolerances become difficult to control. The present invention teaches an alternative method of construction to eliminate the problems with assembly and to significantly reduce the overall product cost.
The present invention concerns a magnetically actuated pushbutton switch wherein each switch includes a pre-assembled, free-standing actuator subassembly. Because each subassembly is separate from the others on a switch panel, they are sometimes referred to herein as island modules. The subassembly is made up of a platform which defines a cavity on its underside. The platform can be either stratified or monolithic. At least a portion of the platform is magnetized. A metallic armature fits into the cavity and is held therein by the magnetic attraction of the magnetized portion of the platform. The stratified platform may comprise a local spacer having a local opening therein, and a coupler which is a magnet. The coupler may have an aperture that allows an actuating button formed on the armature to protrude and receive the actuating force. An upper spacer may surround the protruding button to provide a top surface for supporting a membrane or overlay. The alternate, monolithic platform is formed as a single, integral component. Magnetization of the monolithic platform can take place immediately prior to installation of the subassembly.
The actuator subassemblies are mounted on a substrate. The substrate carries electrodes which include at least one set of switch contacts. In some applications it may be desirable to place a major spacer over the substrate with openings in the major spacer aligned with the switch contacts. The actuator subassemblies are then placed into these openings to complete the switch. The armature may be provided with a lens to disperse backlighting. Tactile domes may be added to the actuator subassemblies. The subassemblies may have multiple armatures.